Boilers are being used for providing heating or hot water in general homes or public buildings. Commonly, boilers use oil or gas as fuels to burn the oil or gas through burners and then heat water by using combustion heat generated during the combustion process to circulate the heated water to indoor spaces, thereby heating the indoor spaces or providing hot water as necessary.
FIG. 1 is a view of a heating and hot water boiler according to a related art.
A heating and hot water combination boiler 1 according to the related art includes a main heat exchanger 10 for heating heating-water by combustion heat of a burner (not shown), a circulation pump 20 for circulating the heating water, a three-way valve 30 that is opened so that the heating water heated by the main heat exchanger 10 is supplied to a heating supply tube 71 in a heating mode and supplied to a hot-water supply heat exchanger 40 in a hot water mode, the hot-water heat exchanger 40 in which the heating water heated by the main heat exchanger 10 is heat exchanged with cold water so as to supply the hot water, a flow rate switch 50 for detecting introduction of the cold water, for example tap water, a temperature sensor 60 for detecting a temperature of the hot water that is supplied to a user, the heating supply tube 71 for supplying the heating water heated by the main heat exchanger 10 to a heating consumption place (not shown), and a returning water tube 72 through which returning water after consuming its heat in the heating consumption place flows.
In case of a condensing boiler, the main heat exchanger 10 is constituted by a sensible heat heat-exchanger 11 that absorbs combustion sensible heat of the burner and a latent heat heat-exchanger 12 that absorbs latent heat of vapor contained in a combustion gas that is heat-exchanged in the sensible heat heat-exchanger 11.
Vertical arrangement of the sensible heat heat-exchanger 11 and the latent heat heat-exchanger 12 of FIG. 1 corresponds to a downward combustion type burner. When an upward combustion type burner is installed, the burner, the sensible heat heat-exchanger, and the latent heat heat-exchanger may be successively disposed from the bottom.
In such a heating and hot water combination boiler according to the related art, in the heating mode, the returning water is directly heated in the main heat exchanger 10 by the combustion heat of the burner, and in the hot water mode, the cold water is indirectly heated in the hot-water supply heat exchanger 40 by using the heating water heated in the main heat exchanger 10, and thus the hot water is supplied to the user.
Generally, if the user intends to use the hot water, the user expects hot water having a desired temperature to come out when he turns on the tap. Also, if the boiler operates to heat the indoor space, it is expected that it takes a predetermined time until an indoor temperature increases.
In the above-described heating and hot water combination boiler according to the related art, since the cold water is indirectly heated in the hot-water supply heat exchanger 40 by using the heating water heated in the main heat exchanger 10 to supply the hot water to the user in the hot water mode, it takes a lot of time to increase the temperature of the hot water up to a temperature desired by the user, and thus it may not satisfy the user's desire to immediately use the hot water having the desired temperature. Also, since more amount of heat is needed in the hot water mode when compared to the heating mode, energy consumption may increase in countries where the hot water is used a lot.
Also, if the user turns on the hot water tap to changes in usage amount of hot water while using the hot water, heat of combustion of the burner is adjusted. However, since the cold water is indirectly heated in the hot-water supply heat exchanger 40, it takes a lot of time until the temperature of the hot water reaches a preset temperature desired by the user even though the heat of the combustion of the burner changes. Also, the hot water may change to a temperature higher or lower than the preset temperature to cause temperature deviation.